Magnets have both north and south poles, and a magnetic field extending between and around the poles. When a mechanical force causes a wire or other electrical conductor to move through a magnetic field, an electric current is induced to flow in the electrical conductor. This is the principle of an electric generator. Conversely, when an electric current flows through a wire or other electrical conductor, a magnetic field is created around the conductor, and if the conductor is in an existing magnetic field, the magnetic field around the conductor interacts with the existing magnetic field to create a mechanical force that tends to move the conductor. This is the principle of an electric motor. Electric generators convert mechanical force into electric current, and electric motors convert electric current into mechanical force.
Conventional electric generators and conventional electric motors have a rotating portion called the rotor, which rotates within or adjacent to a stationary structure called the stator. Magnets (either permanent magnets or electromagnets) are placed on the rotor, and conducting wire is placed in the stator, or vice versa. The wire is usually wound (preferably, around cores, but optionally without cores) to form coils of wire that are (at least in part) at right angles to the axis of rotation of the rotor, because the lines of the magnetic field created by an electric current are at right angles to, and rotate around, the direction of flow of the current: under the “right hand rule”, if your right thumb points along the direction of electric current, then your right hand's fingers show the direction of the magnetic field lines extending from the north pole to the south pole.
Thus, in an electric generator, a mechanical force that causes the magnets in the rotor to rotate, induces an electric current to flow through the wires in the coils in the stator, thus generating an electric current to flow through those wires. In an electric motor, an electric current flowing through the wires in the coils in the stator creates a magnetic field, thus creating a force against the magnets in the rotor that causes the rotor to rotate. In both electric generators and electric motors, the magnets can be in the stator and the coils can be in the rotor instead.
It should be noted that electric current is conventionally characterized as the direction of positive charge (such as the positive terminal of a battery), which is the opposite of the direction of actual flow of negatively charged electrons: electrons actually flow towards the negative terminal of a battery. The voltage of an electric current is the pressure of the electron flow, and can be negative, when electrons are flowing one way (towards the negative terminal), or positive, when electrons are flowing the other way. If electrons are not flowing, there is no electric current, and therefore no voltage. When electrons flow in only one direction, this is called direct current. Direct current can be either negative or positive, depending on which way the electrons are flowing.
When electrons flow in one direction, and then in the opposite direction, this is called alternating current, because the voltage alternates from negative to positive.
Alternating current is important for transmitting electricity, because energy can be transmitted much more efficiently using alternating current than using direct current, especially at high voltages. This is why electricity provided by electric utilities is usually alternating current, and why long distance electric transmission lines are at high voltages.
Many alternative energy generating technologies, such as solar photovoltaic cells, inherently create direct current, which must then be changed to alternating current using an “inverter.” Many types of devices, such as battery chargers, use direct current, so alternating current is often changed to direct current using a “rectifier.”
Electricity must be used in a circuit, where electricity flows from one part of the circuit (usually a battery or generator creating a voltage that pushes an electric current), all the way through the remainder of the circuit, and returns to its origin (the battery or generator). The amount of energy that can be extracted from any electric current, whether direct or alternating, depends on the difference in voltages (electric pressure) between one part of the circuit (through which the current is flowing), and another part of the circuit, and also on the amount of current that is flowing—the greater the difference in voltages between the two parts of the circuit, and the greater the current flowing at those voltages, the more energy can be extracted from the circuit.
The remainder of this disclosure will discuss electric generators, but the person having ordinary skill in the art (“ordinary artisan”) would recognize that this disclosure is also applicable to electric motors, when run in reverse.
Conventional electric generators are designed so that the direction of electron flow, and therefore the polarity of the electric current, reverses at a certain point or points during each turn of the rotor, to create alternating current. However, this alternating current creates drag or “cogging” due to the interactions of the reversing current flow with the magnets in the generator. Also, substantial energy is lost because current flow causes magnetization of the cores of the coils, and reversal of that current flow causes demagnetization and then opposite magnetization of those cores, which wastes energy. This “cogging” in a wind generator means that higher wind speeds may be required to start the generator rotating, thus raising the “start up speed.” Further, a wind generator may not be able to provide useful power until a minimum “cut in speed” of the wind generator has been reached.
If the generator of this invention is used in a wind generator or other application in which the rotational speed of the rotor/stator assemblies will vary, then the frequency and voltage of the alternating current from the coils of the rotor/stator assemblies will vary with the wind speed, which may not provide useful power. In such an application, it would be preferable to connect the alternating current from the rotor/stator assemblies (which has uncontrollably varying frequency and voltage) to a rectifier, to provide useful DC current. However, the rectifier may not be able to provide useful DC current unless it is provided with a minimum amount of alternating current.
It should be noted that, if the present invention is used as a wind generator, it is preferred to use an electromagnetic brake to slow down rotation at excessive speed.
Because magnets always have both north and south poles, and because the goal is usually to make engines and generators smaller, and because magnets must be close to the coil/wire to maximize current flow, in most configurations of magnets and coils, the same portion of the coil/wire is exposed to successive north and south poles of the magnets, which also causes reversal of current flow. For example, a magnet in a rotor will pass by a coil in a stator, by having the north pole pass by first, then the south pole (or vice versa).
U.S. Pat. No. 9,331,534 to Yost, incorporated herein by this reference, discloses a magnetic generator for modular micro wind turbines with axially aligned magnets on each side of the rotor face. As a drive shaft rotates the rotors in proximity to stators, a magnetic flux and electricity is generated. Yost teaches that magnets should be separated by 0.04 to 0.6 inches to achieve “magnetic amplification”: the closer the magnets, the higher the energy output (see col. 15, line 38, to col. 16, line 35, and FIGS. 56-61).
Published U.S. patent application Ser. No. 14/290,741 to Oelofse discloses a generator design using a modified Halbach Array.